1. Field of the Invention
The present invention relates to a rodless piston and cylinder assembly, and, more particularly, to improvements in such an assembly where the piston reciprocates a working member through a cable attached to the piston and extending out of the ends of the cylinder to the working member.
The present invention pertains to improvements in the cable and in the means for braking the working member, particularly where the working member is in the form of a reciprocating carriage.
2. State of the Prior Art
Generally there are two types of rodless piston actuators. In one type a cable is attached to one end of the piston and passes out of the cylinder around a pulley to one end of an actuator. Another cable portion is attached to the other end of the piston and passes out the cylinder around a pulley and is attached to the other end of the actuator. The actuator then moves in synchronism with, but in the opposite direction from the piston. Typically the cable is a multi strand wire rope which may or may not be coated. Appropriate seals are used where the cable passes through the cylinder.
In another type of rodless piston, the actuator is attached to the piston and passes radially outward through a slot in the cylinder. A flexible seal closes the slot along the length of the cylinder and must move to permit movement of the actuator.
In both types of rodless pistons, braking of the system is most often accomplished between the piston and the cylinder. Many of these devices utilize a wedge carried by the piston which brakes against only one side of the cylinder causing a force concentration which tends to gall the surface of the cylinder wall eventually necessitating expensive repair or replacement of the cylinder. There have been many improvements over this basic system such as that set forth in U.S. Pat. No. 4,471,686 assigned to Greenco Corporation, the Assignee of this present invention wherein a double acting piston has two sliding members which accomplish the braking around the entire periphery of the cylinder.